Americans for Prosperity is launching a major ad buy hitting Sen. Mark Pryor (D-Ark.) on Thursday, pushing the group’s advertising spending in the race to more than $1.4 million so far this year.

Pryor, who is facing off with Rep. Tom Cotton (R-Ark.) in one of the most hotly contested races of the year, was the subject of a six-figure negative ad buy last month from the outside conservative group. The buy for second batch of ads, shared first with POLITICO, totals about $700,000 and links Pryor to cancelled insurance plans tied to Obamacare.

“We received a letter from our insurance company as of December of 2014 that we would no longer be covered by Blue Cross Blue Shield,” says a woman named Wanda in the ad. “Well, now, when somebody tells you, ‘If you like it, you can keep it,’ you believe them. But that’s not so in this case.”

The 30-second spot from the Koch brothers-backed group is set to air statewide on cable and networks, along with digital advertising, for three weeks. Text at the end reads, “Senator Mark Pryor voted for Obamacare. Tell Sen. Pryor, Obamacare hurts Arkansas families.”

“You think you’re going to be just one of those unlucky people, but then you find out it’s happening to so many,” Wanda says. “And again, that’s why so many need to stick together because there is strength in numbers.”

Republicans trying to net the six seats needed to take back control of the Senate view Pryor as one of their top targets, and have been hammering him over the health care law.

Pryor spokesman Erik Dorey pushed back in a statement that blasted Cotton’s positions on Medicare, student loans and income equality for women, and said “Arkansans won’t be distracted” by that record, “even by the Koch brothers spending secret millions to reward his recklessness that harms Arkansas families.”

AFP has spent considerable sums in other battleground states, including North Carolina and Louisiana.

“There are thousands of other Arkansans like Wanda who have been hurt by this law, and millions more across the country,” AFP head Tim Phillips said in a statement. “It’s time for Senator Pryor to admit that that Obamacare is hurting Arkansas families.”